High lift leading edge device

ABSTRACT

The retractable leading edge wing flap has a skin surface with tapered thickness in order that it can more easily assume the desired nonuniform degree of curvature when the flap is in its extended position. Through the inherent resilency of the flap skin surface material in combination with an actuating mechanism having a minimum of operating elements, the surface of the flap is provided with a variable contour thereby producing a variable camber to the flap panel and likewise to the wing airfoil section that is in combination therewith. More specifically, the flap extension and retraction mechanism operates in a chordwise plane and requires a maximum of five links to produce the desired result. Further, the actuating mechanism operates to position the flap panel relative to the fixed wing leading edge so as to vary the wing airfoil section aerodynamic flow characteristics by changing the total overall amount of effective wing camber. For the landing condition, the arrangement of the linkage mechanism produces an angular relationship of the flap chord plane relative to the wing chord plane such that the overall aerodynamic affect is a greater airfoil section camber at said landing condition than at the take off condition. Also, the arrangement of the linkage mechanism for the landing condition is such that the leading edge wing flap is extended further forward from the relatively fixed leading edge of the main wing section in addition to being spaced away from the wing leading edge, to form an aerodynamic slot; whereas, at the take off position the movable flap section and wing leading edge are in abutment relation thereby forming a substantially continuous upper surface without the slot.

United States Patent 1 Gorges 1 HIGH LIFT LEADING EDGE DEVICE FriedrichJ. Gorges, Dietzenbach-Steinberg, Germany [75] Inventor:

[73] Assignee: The Boeing Company, Seattle, Wash. [22] Filed: June 30,1971 [21] Appl. No.: 175,987

3,363,859 Watts 244/42 CA Primary Examiner--Milton Buchler AssistantExaminerCarl A. Rutledge Attorney-Glen Orlob [57] ABSTRACT Theretractable leading edge wing flap has a skin surface with taperedthickness in order that it can more easily assume the desired nonuniformdegree of curvature when the flap is in its extended position. Through[451 July 3,1973

the inherent resilency of the flap skin surface material in combinationwith an actuating mechanism having a minimum of operating elements, thesurface of the flap is provided with a variable contour therebyproducing a variable camber to the flap panel and likewise to the wingairfoil section that is in combination therewith. More specifically, theflap extension and retraction mechanism operates in a chordwise planeand requires a maximum of five links to produce the desired result.Further, the actuating mechanism operates to position the flap panelrelative to the fixed wing leading edge so as to vary the wing airfoilsection aerodynamic flow characteristics by changing the total overallamount of effective wing camber. For the landing condition, thearrangement of the linkage mechanism produces an angular relationship ofthe flap chord plane relative to the wing chord plane such that theoverall aerodynamic affect is a greater airfoil section camber at saidlanding condition than at the take off condition. Also, the arrangementof the linkage mechanism for the landing condition is such that theleading edge wing flap is extended further forward from the relativelyfixed leading edge of the main wing section in addition to being spacedaway from the wing leading edge, to form an aerodynamic slot; whereas,at the take off position the movable flap section and wing leading edgeare in abutment relation thereby forming a substantially continuousupper surface without the slot.

6 Claims, 6 Drawing Figures Patented July 3, 1973 .2 Sheets-Sheet lAWE/VT Patented July 3, 1973 3,743,219

2 Sheets-Sheet 8 HIGH LIFT LEADING EDGE DEVICE SUMMARY OF THE INVENTIONThe invention relates to a high lift leading edge device for producing avariable camber airfoil section for the wing of an aircraft and moreparticularly to the articulating mechanism for moving the leading edgeflap device from its retracted positionin the lower surface of the wing,to its extended position in front of the wing thereby increasing thewing chord and forming an increase in the aerodynamic camber of thecombined flap and wing airfoil section for improving liftcharacteristics for slow speed flight such as take off or landing. Whenthe leading edge flap device is in its retracted position, its surfacecontour is somewhat flattened to conform to the desired aerodynamicshape of the undersurface of the fixed wing airfoil section whereas,when the leading edge device is in its extended position it has a curvedsurface contour that improves the aerodynamic characteristics of theincreased chord and camber of the wing. Also, when the leading edge flapis in the extended position, it is further positionable from a gap, to ano-gap relationship with respect to the leading edge of the fixed wingportion, for further varying the aerodynamic characteristics of theoverall wing section.

It is generally known that in extensible leading edge slat devices, theslat contours are generally dictated by the desired high speed airfoilsection at an efficient cruise condition and that the individual slatcomponents form an integral part of the forward section of the wing whenin their retracted position; the contour of which does not change whenextended. Therefore, the overall external contour of the slat does notprovide the most desirable aerodynamic shape when it is extended forwardand downward to increase the wing chord and camber for maximum low speedperformance. Further, the mechanism for positioning the slats such astracks and rollers are not entirely trouble free due to wing bendingloads. Further, they are time consuming to adjust and therefore costlyto operate.

Generally, the variable camber leading edge flaps, such as those used onthe Boeing 747 type airplane, have a contoured aerodynamic shape butthey are not positionable to provide a gap or no gap aerodynamic slotbetween the flap segment and the leading edge of the main wing. Also,some have a separate bullnose which does not present a continuouschordwise frontal surface but results in a continuous spanwise seamexposed to the airflow. In addition, the actuating mechanism generallyrequires a larger number of parts than the present invention.

An object of the present invention is to provide a wing leading edgeflap system with a greater coefficient of lift during low speedoperation such as take off or landing than the existing systems provide,without compromising the airfoil shape required for high speedoperation.

Another object is to provide a wing leading edge with optimum airfoilshape leading edge flap system for take off and landing operation byproviding a variable camber wing flap with two operative extendedpositions in combination with a different degree of camber at each ofsaid operative positions.

One of the advantages of the present invention, is that the wing leadingedge flap actuating mechanism has relatively few parts thereby providingfor minimal maintenance and cost which makes it ideally suitable for usein the modification of existing airplanes as well as in new airplanedesign.

These, as well as other objects and advantages of the invention, will bemore clearly understood from the following description when read withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a chordwise cross sectionalview of the variable camber leading edge wing flap and its extension andretraction linkage mechanism shown in the retracted or cruise position.

FIG. 2 is a chordwise cross sectional view, taken at a differentspanwise location from that of FIG. 1, showing the powered actuationsystem for the high-lift leading edge'device positioned in its stowed orcruise position.

FIG. 3 is a view similar to FIG. 1 with the leading edge flap panelmoved slightly out from its stowed position.

FIG. 4 is a view similar to FIG. 1 with the leading edge flap panel inthe landing condition including an aerodynamic slot.

FIG. 5 is a view similar to FIG. 1 with the leading edge flap panelarranged in the take off condition with a no-gap relationship to theleading edge of the main wing.

FIG. 6 is a sectional top view taken along the lines 6--6 of FIG. 5 inthe direction indicated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The leading edge high liftsystem of the present invention comprises a variable camber leading edgewing flap having a chord-wise arranged extension and retraction linkagemechanism in combination with a powered actuation system.

FIGS. 1 to 6 depict the preferred embodiment of the present inventioncomprising a five linkage mechanism in a chord-wise plane. For eachspanwise set of linkage mechanism, the lower skin surface of the wingleading edge or flap panel 20 is pivotally suspended from the relativelyfixed wing section 22 by two structural attachment points, 24 forwardand 26 aft. The flap panel 20 in its retracted position as shown in FIG.1, completes the undersurface nose portion or airfoil profile of themain fixed wing of the airplane and allows a desired cruise wing contourwhen retracted. The flap panel 20 may be composed of a glass fibermaterial, a honeycomb sandwich composite, a flexible preformed metal,etc., that is designed to produce the desired aerodynamic contour whenthe flap is in its stowed or retracted position. To produce the properdegree of aerodynamic curvature in one of the operative extendedpositions, the skin thickness is designed to be tapered chordwise suchthat when flexed by the linkage mechanism as hereinafter described, itproduces the proper amount of camber 28 with respect to the flap chordplane 30'. Also, the variation in thickness of the flap skin from thelesser thickness at the bullnose 32 or leading edge of the flap panel toa greater thickness towards its trailing edge, determines to a greatextent the flap chordwise position at which the greatest amount ofcamber occurs. In the present invention it occurs forward ofapproximately the thirty percent flap chord point.

When the flap is in one of its operative extended positions, such as thelanding position shown in FIG. 4, an aerodynamic slot 34 is createdbetween the flap trailing edge and the leading edge of the relativelyfixed wing. When the flap is in its most forward operative position,such as the take off position shown in FIG. 5, the aerodynamic slot 34is closed off and a substantially continuous upper wing surface ispresented to the oncoming airstream.

FIG. 2 depicts an actuation system embodiment for the high lift leadingedge device. The arrangement of the power hinge mechanism is shown withthe leading edge flap in its retracted cruise position as illustrated inFIG. 1. The actuation system shown in FIG. 2 comprises a linear actuator36 having its housing pivotally attached at 38 to fixed wing leadingedge structure and its actuator rod 40 pivotally connected at 42 to theupper terminal of rocker arm 44. The lower end of rocker arm 44 ispivotally mounted at 46 to a bracket 48 which is attached to the frontwing spar 50. Also, connected to the common pivot 42 is the upperterminal of connector link 52 which is pivotally connected at its lowerterminal 54 to the torque arm 56. The rocker arm 44 carries the fulcrum42 of the connector link 52 which rotatably drives the torque tube 26 bymeans of the torque arm 56. The torque arm 56 is fixedly mounted ontorque tube 26 which in turn is rotatably supported by the relativelyfixed wing structure. In operation, to extend the flap panel 20, thelinear actuator 36 contracts thereby, rotating rocker arm 44counterclockwise which in turn through the common pivotal connection 42and connector link 52, rotates the torque arm 56 and the torque tube 26through approximately 170 counterclockwise, which in turn is sufficientto operate the leading edge flap through to the desired positions ashereinafter described.

FIGS. 1, 3 to are chordwise cross-sectional views of the preferredembodiment of the variable camber leading edge wing flap of the presentinvention and its extension and retraction linkage mechanism at variousstages of operation.

In the operation of positioning the leading edge flap 20 from the stowedposition shown in FIG. 1, through the intermediate position shown inFIG. 3, to the first of two operating positions namely, the landingposition shown in FIG. 4, the linear actuator 36 through operation oflinkage mechanism as described and shown in FIG. 2 rotates the driveshaft 26, which in turn rotates the bellcrank 60 counterclockwise aboutthe aft structural attachment pivot 26.

As shown in FIG. 4, the shorter driving arm 60A of the bellcrank 60 ispivotally connected at 62 to the aft end of lever 64 and the longerdriving arm 608, forming an angle of approximately 25 degrees with thatof the shorter arm 60A, is pivotally connected at 66 to link 68. Theother end of lever 64 connects to the flap panel 20 toward its trailingedge at pivotal connection 70. The lever 64, is supported at anapproximate midlength position at pivotal connection 72, to the lowerterminal of rocker arm 74 which swings about the fixed wing structurallypivot 24. The lever 64, at a point slightly inboard from its forwardend, carries the fulcrum 76 of the flap chord lever 78. The flap chordlever 78 is driven to rotate about pivotal connection 76 by means of thelonger driving arm 60B of the bellcrank 60 acting through connectinglink 68 pivotally interconnected therewith through pivots 69 and 66, toextend and retract the flap panel 20. As the bellcrank 60 rotatescounterclockwise from the stowed "position of the flap as shown in FIG.I, it pushes links 64 and 68 pivotally connected thereto at 62 and 66respectively, forwardly and downwardly through the guiding action ofrocking lever 74. The flap system initially rotates around point 24 torelease the trailing edge of the flap panel from the under wing surfaceas shown by the intermediate position of the linkage in FIG. 3. Further,it will be noted that at this intermediate position, the flap chordwisepivotal connections 80, 70 and 76 are substantially in alignment suchthat the flap skin is at a lesser camber position, the least camberposition being the stowed condition shown in FIG. 1. The flap skin 20 isattached through its leading edge bullnose 32 to one end of chord lever78 at pivotal connection 80 and the trailing edge of the flap skin 20 isindirectly connected at 70 to the other end of chord lever 78 through asection or element 64A of lever 64 that extends between points 70 and76. This section 64A in combination with chord lever 78 forms a scissorsor toggle linkage arrangement having its fulcrum at 76. As the flappanel 20 rotates clockwise from its stowed position, this scissorslinkage arrangement contours the flap skin 20 to give camber 28 to theflap panel, due to the foreshortening that takes place between points 80and 70. The flap chord lever 78 is mounted to rotate clockwise withrespect to link 64 about point 76 as the flap is forwardly extended; andas it does, point 70 moves towards point 80 which applies a bendingforce to the flap skin to increase its curvature and likewise itscamber. This curved flap surface provides a desirable aerodynamic flowover the combined flap and leading edge surface of the fixed wing 22 toprevent separation of the airflow on the upper wing surface.

When the flap panel 20 is in the operative landing position shown inFIG. 4, an aerodynamic gap 34 is cre ated between the trailing edge ofthe flap panel 20 and the leading edge of the wing 22 which improves itsslow speed aerodynamic performance.

The operation of the flap to the take off position is obtained bycontinuing rotation of the drive bellcrank 60 in the same directionthrough the landing position shown in FIG. 4 to the take off positionshown in FIG. 5. As the flap system rotates past the landing position tothe take off position, the flap skin camber 28 is further increased andthe aerodynamic gap is closed off thereby providing a lower overalltotal wing airfoil camber but with an improved aerodynamic flowcharacteristic for the take off condition. The leading edge flap extendsthe effective wing chord and through the sealing of the aerodynamic gapand increased skin curvature of flap gives better coefficient of lift byvirtue of its aerodynamic shape.

The bullnose 32 or leading edge of theflap panel functions as a unitizedpart of the flap panel through its pivotal linkage connection and aidsin flexing the skin of the flap panel to its aerodynamic contour asshown in the extended operative positions of FIGS. 4 and 5. All of theparts involved are geometrically arranged to enable the bullnose 32 as arigid portion of the flexible flap, to move clear in and out of thefixed structure forward of the front spar location. As the last part ofthe motion during retracting the bullnose 32 contacts the seal 82.

While the invention has been disclosed with reference to a preferredembodiment, it is to be understood that those modifications and changeswhich become obvious to a person skilled in the art as a result of theteachings hereof will be encompassed by the following claims:

What is claimed is:

1. A variable camber flap for the leading edge of an airfoil comprising:a flexible flap panel supported from the leading edge portion of theairfoil in an operative forwardly and downwardly extending position; abellcrank pivotally supported at its main pivot from the leading edgeportion of the airfoil about a fixed hinge line for rotation in achordwise plane; a guide link forward of the bellcrank having upper andlower terminals, pivotally connected at its upper terminal to theleading edge portion of the airfoil; a main flap support link, fore andaft extending, pivotally connected at its aft terminal to a first arm ofthe bellcrank, pivotally connected at its forward terminal to thetrailing edge portion of the flap and pivotally supported atapproximately its mid-point to the lower terminal of the guide link; aflap chord link pivotally supported at its upper terminal from a forwardportion of the main flap support link and pivotally connected at itslower terminal to the leading edge portion of the downwardly andforwardly extending flap; an interconnecting link, fore and aftextending, pivotally connected at its forward terminal to anintermediate portion of the flap chord link and pivotally connected atits aft terminal to the other arm of the bellcrank; and actuating meansfor rotating the bellcrank about its main pivot causing the flap to beretracted from its operative forwardly and downwardly extendingposition, into the under surface of the airfoil.

2. The structure as set forth in claim 1, wherein said flexible flappanel has a tapered skin thickness in a chordwise plane from a lesserthickness towards the leading edge of the flap panel to a greaterthickness towards its trailing edge when the flap is in an operativeforward extended position.

3. The structure as set forth in claim 1, wherein said fexible flappanel is positionable with respect to the leading edge of said airfoilso as to form an aerodynamic slot between the trailing edge of the flappanel and the leading edge of said airfoil when the flap is in a firstoperative forward extended position.

4. The structure as set forth in claim 3, wherein said flexible flappanel is further positionable with respect to the leading edge of saidairfoil so as to form an abutment relation between the trailing edge ofthe flap panel and the leading edge of said airfoil to form asubstantially continuous upper surface when the flap is extended furtherforward than said first operative forward extended position to a secondextended position.

5. The structure as set forth in claim 4, wherein said flexible flappanel has less camber when in said first operative forward extendedposition than in said second extended position.

6. The structure as set forth in claim 5, wherein said flexible flappanel when in said first operative forward extended position has itschord plane positioned relative to chord plane of said airfoil such thata greater aerodynamic camber of the flap and airfoil combination isproduced than at said second extended position.

1. A variable camber flap for the leading edge of an airfoil comprising:a flexible flap panel supported from the leading edge portion of theairfoil in an operative forwardly and downwardly extending position; abellcrank pivotally supported at its main pivot from the leading edgeportion of the airfoil about a fixed hinge line for rotation in achordwise plane; a guide link forward of the bellcrank having upper andlower terminals, pivotally connected at its upper terminal to theleading edge portion of the airfoil; a main flap support link, fore andaft extending, pivotally connected at its aft terminal to a first arm ofthe bellcrank, pivotally connected at its forward terminal to thetrailing edge portion of the flap and pivotally supported atapproximately its mid-point to the lower terminal of the guide link; aflap chord link pivotally supported at its upper terminal from a forwardportion of the main flap support link and pivotally connected at itslower terminal to the leading edge portion of the downwardly andforwardly extending flap; an interconnecting link, fore and aftextending, pivotally connected at its forward terminal to anintermediate portion of the flap chord link and pivotally connected atits aft terminal to the other arm of the bellcrank; and actuating meansfor rotating the bellcrank about its main pivot causing the flap to beretracted from its operative forwardly and downwardly extendingposition, into the under surface of the airfoil.
 2. The structure as setforth in claim 1, wherein said flexible flap panel has a tapered skinthickness in a chordwise plane from a lesser thickness towards theleading edge of the flap panel to a greater thickness towards itstrailing edge when the flap is in an operative forward extendedposition.
 3. The structure as set forth in claim 1, wherein said fexibleflap panel is positionable with respect to the leading edge of saidairfoil so as to form an aerodynamic slot between the trailing edge ofthe flap panel and the leading edge of said airfoil when the flap is ina first operative forward extended position.
 4. The structure as setforth in claim 3, wherein said flexible flap panel is furtherpositionable with respect to the leading edge of said airfoil so as toform an abutment relation between the trailing edge of the flap paneland the leading edge of said airfoil to form a substantially continuousupper surface when the flap is extended further forward than said firstoperative forward extended position to a second extended position. 5.The structure as set forth in claim 4, wherein said flexible flap panelhas less camber when in said first operative forward extended positionthan in said second extended position.
 6. The structure as set forth inclaim 5, wherein said flexible flap panel when in said first operativeforward extended position has its chord plane positioned relative tochord plane of said airfoil such that a greater aerodynamic camber ofthe flap and airfoil combination is produced than at said secondextended position.